Phase transition in reconstituted chromatinT. Nakai1, K. Hizume2, S. H. Yoshimura2, K. Takeyasu2 and K. Yoshikawa1
1 Department of Physics, Graduate School of Science, Kyoto University & CREST Kyoto 606-8502, Japan
2 Graduate School of Biostudies, Kyoto University - Kyoto 606-8502, Japan
received 23 August 2004; accepted in final form 20 January 2005
published online 11 February 2005
By observing reconstituted chromatin by fluorescence microscopy (FM) and atomic force microscopy (AFM), we found that the density of nucleosomes exhibits a bimodal profile, i.e., there is a large transition between the dense and dispersed states in reconstituted chromatin. Based on an analysis of the spatial distribution of nucleosome cores, we deduced an effective thermodynamic potential as a function of the nucleosome-nucleosome distance. This enabled us to interpret the folding transition of reconstituted chromatin in terms of a first-order phase transition. This mechanism for the condensation of chromatin is discussed in terms of its biological significance.
87.15.He - Dynamics and conformational changes.
64.75.+g - Solubility, segregation, and mixing; phase separation.
36.20.Ey - Conformation (statistics and dynamics).
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